In-ear earphones, including wireless in-ear earphones and smart wireless in-ear earphones, are getting more popular since they can deliver fair sound quality while keeping small size and light weight. The challenge is to reproduce high sound quality while keeping the power consumption low, as these hearing devices operate with rechargeable batteries or are connected to a device which operates with a rechargeable battery. In order to deliver a high quality sound with wide band audio signal to the human eardrum professional in-ear monitors of today apply a plurality of receivers. As an example professional/premium in-ear monitors apply at least two balanced armature receivers where the audio signal from both receivers are filtered and combined in order to cover a wide audio bandwidth.
U.S. Pat. No. 7,194,103 B2 discloses an in-ear monitor comprising a moving coil receiver and a balanced armature receiver. The moving coil receiver is used as a woofer and thus provides a frequency response in a lower frequency band, whereas the balanced armature receiver is used as a tweeter and thus provides a frequency response in a higher frequency band. However, it is well established that balanced armature receivers are only efficient around their resonance frequency which typically is located in the speech frequency range, i.e. in the mid frequency range. Thus, the arrangement suggested in U.S. Pat. No. 7,194,103 B2 has its limitations in that it is not able to reproduce for example audio sound in the high frequency band.
The missing high frequency band is not compatible with hearing devices of today which should be able to perform both speech and music reproduction, the latter involving high frequency sound reproduction. Thus, the in-ear monitor suggested in U.S. Pat. No. 7,194,103 is not able to comply with this demand. Thus, there is a need for hearing devices having a broad frequency response.
U.S. Pat. No. 9,055,366 addresses a three-band speaker arrangement, i.e. woofer, mid and tweeter, where each speaker covers one frequency band. The tweeter is a balanced armature speaker, whereas the mid and/or woofer may be either balanced armature speakers or moving coil speakers. However, it is a disadvantage of the speaker system suggested in U.S. Pat. No. 9,055,366 that a total of three speakers is required to cover the complete frequency band in order to reproduce high quality audio sound.
US 2006/133636 A1 discloses a method for optimizing the audio performance of an earpiece which combines two drivers within a single earpiece. In this invention, each driver uses a discrete sound delivery tube. The focus in this patent application is to optimize the audio performance of wired earphones and hence not considering the energy saving optimization in wireless earpieces.
US 2011/058702 A1 discloses a multi driver in-ear monitor device (wired or wireless) with several embodiments to design tubing. The main focus in in-ear monitors are the high sound quality and optimizing delays between transmitter and receiver. This patent application does not deal with energy efficiency.
US 2014/205131 A1 discloses use of two balanced armature receivers in an earbud cup housing and several designs of the tubing to combine and improve the audio output quality of the drivers. In this disclosure, the difference between speech and music and also the energy efficiency of the battery operated earbuds are not addressed.
In the prior art references mentioned above, the drivers and balanced armature receivers are all driven at the same time and they are functioning together. The above-mentioned prior art references all target the music reproduction in the ear canal and do not distinguish between speech and music.
It may thus be seen as an object of embodiments of the present invention to provide a simple hearing device with enhanced acoustical performances.
It may be seen as a further object of embodiments of the present invention to provide a power saving hearing device.
It may be seen as a still further object of embodiments of the present invention to provide an augmented hearing device which is able to save power by selecting an appropriate number of receivers using a switching functionality.